1. Field of the Invention
The present invention relates to a resist composition and a process for forming a resist pattern.
More particularly, the present invention relates to a resist composition containing a certain copolymer and a photo acid generator and also relates to the process for forming the resist pattern having a high sensitivity and a good dry etch resistance.
2. Description of the Related Art
Due to the necessity of treating a large amount of information at a high speed on an integrated semiconductor device, which plays a main role in an information treating device, large-scale integrated circuits (LSI) and very large-scale integrated circuits (VLSI) have been developed and are now in practice.
This integration is carried out by the miniaturization of unit elements such as wiring patterns and electrodes. At present, the use of submicron minimum line spacing in the wiring pattern is common.
When forming a fine resist pattern, ultraviolet lights were employed as an exposure light source at the beginning of the photolithography. Due to limitations in the use of wavelength, an exposure process using deep ultraviolet lights are carried out.
Here, the exposure light source that radiates deep ultraviolet lights as mentioned can be a high pressure mercury lamp or an excimer laser.
However, there is the problem that the power of the high pressure mercury lamp is low, in the wavelength region of the deep ultraviolet light.
Therefore, the use of a large power excimer laser (for instance, when KrF is used, the wavelength is 248 nm) has been considered as the exposure light source.
However, even if the excimer laser is employed, the prior resist composition cannot be used, because said resist absorbs too much deep ultraviolet light, so that the said resist results in sloped wall profiles and poor resolution.
Therefore, practical use of such a resist composition having a high resolution and capable of being applied to the above wavelength light is desired.
In the conventional resist composition, many kinds of resists containing an aromatic ring (such as a benzene ring) so as to obtain good dry etch resistance, for instance, a phenol novolak resin, have been developed as a base polymer.
However, the resist containing an aromatic ring absorbs far too much deep ultraviolet light, so that a fine pattern corresponding to miniaturization in the patterning process using deep ultraviolet lights as an exposure light source cannot be obtained.
On the other hand, as a KrF excimer resist, the resist including an acrylate polymer such as poly t-butylmetacrylate as a base polymer has been studied but, it was found that said polymer did not display good dry etch resistance because of the lack of the aromatic ring.
Therefore, practical use of such a resist composition having good dry etch resistance and good transparency, in which the polymer lacks an aromatic ring is strongly desired.
The necessary requirements for the resist that can be adopted for use in the region of an deep ultraviolet light are as follows:
1) Minimal absorption in the region of deep ultraviolet lights and having a high resolution; PA1 2) High sensitivity; and PA1 3) Superiority in dry etch resistance. PA1 100 parts by weight of a copolymer consisting of a 2-norbornene-2-substituent unit and an acrylic acid ester unit of the formula I; ##STR2## wherein, X is a cyano or chloro group, R is tert-butyl, dimethylbenzyl, or tetrahydropyranyl, m is an integer of 9 to 2390, and n is an integer of 21 to 5180, and 1 to parts by weight of a photo acid generator. PA1 coating a substrate to be fabricated with a resist composition comprising 100 parts by weight of a copolymer consisting of a 2-norbornene-2-substituent unit and an acrylic acid ester unit of the formula I; ##STR3## wherein, X is a cyano or chloro group, R is tert-butyl, dimethylbenzyl, or tetrahydropyranyl, m is an integer of 9 to 2380, and n is an integer of 21 to 5180, and 1 to 20 parts by weight of a photo acid generator, PA1 drying the resist composition to form a resist coating, PA1 exposing the resist coating selectively to a predetermined pattern of radiation to form a latent image in the resist layer corresponding to the radiation pattern, and PA1 baking the resist coating, followed by developing the pattern-wise exposed resist coating with a developer to form a resist pattern. PA1 a diaryl indonium salt such as ##STR5## and ##STR6## and an aryl sulfonium salt, for example, triaryl sulfonium salts such as ##STR7## and ##STR8## sulfonic acid derivatives, for example, sulfonic acid esters such as ##STR9## and halogen-containing compounds such as ##STR10##
However, a resist fully satisfying the above requirements has not yet been developed.
Therefore, there is a need to develop a resist that satisfies the above requirements and to apply said resist.